Comment by radiowave

3 years ago

An interesting complicating factor here is that much of the UK's installed base of CCTG stations were built during the 90s with the intention of replacing many of the smaller coal-fired stations, which would typically be doing 2-shift operations (i.e., day and evening). Now, those CCGT stations are increasingly used to counterbalance renewables, and (as you point out) are now running on much shorter cycles than they were designed for.

A report from a few years back (which I'm afraid I've utterly forgotten the source) examined the data on this, and argued that as a result of this changed pattern of use, these CCGT stations were now not achieving nearly the kind of efficiency figures they were designed for, which from a carbon point of view is not good news - we might still be emitting lots of the stuff, but just not getting as much practical benefit from it as we used to.

Now, I'm not meaning to suggest that this is a disaster, or that is somehow invalidates the entire of concept of renewables, but it does point to the need to be careful about what we take to be a useful measure of progress - and that merely the quantity of supply to the grid in GWH isn't necessarily it.

And the article under discussion here is of course picking away at another strand of this same idea - when we connect these generators together, it gives rise to system-level effects, and we need to be thinking about the outcomes, both beneficial and harmful, in system-level terms as well.

(Edited for spelling.)

7 comments

radiowave

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dTal  3 years ago

The only thing that matters for climate change is the amount of gas burned - the efficiency with which we turn it into work is irrelevant. If we reduce the amount of gas burned, at a cost of burning the remaining gas less efficiently, that's still a win.

In a certain sense one should expect lowering usage to inevitably lower efficiency, as a sort of inverse corollary to Jevon's paradox (which states that as efficiency rises, total usage does too).

  • eru  3 years ago

    You are right up to a point.

    The problem is that building wind turbines in Britain has opportunity costs.

    For simplicity: assume a status quo of 100% gas. We are burning 100 units of gas for that per year.

    Now assume by building a crazy amount of wind turbines we could satisfy 95% of the UK's power demand with renewable. However, for the remaining 5% we'd need to burn 50 units of gas.

    In this scenario, efficiency of burning gas drastically plummeted, but so did overall gas use.

    However now the question is: for the resources invested into building all those turbines, could we have gotten a better climate bang than 50 units of gas saved?

    (All numbers made up, obviously. In practice, we can probably make the economics work. Though we might need to deregulate the grid. It's crazy to pay wind turbines for not running. At least mine bitcoin or smelt aluminum or something.)

Reason077  3 years ago

It won't be long (perhaps in the next 2-3 years) before the UK grid will be able to operate for periods without any CCGTs running at all. We've already come quite close this winter, with record low CCGT output and record high wind turbine production.

Wind turbine output, although variable, is also fairly predictable: so good modelling and scheduling should ensure that when CCGTs do operate, they can run as efficiently as possible and not be spinning up and down too frequently.